Encapsulated micro-electro-mechanical device, in particular a mems acoustic transducer

ABSTRACT

An encapsulated micro-electro-mechanical device, wherein a MEMS chip is encapsulated by a package formed by a first, a second, and a third substrates that are bonded together. The first substrate has a main surface bearing the MEMS chip, the second substrate is bonded to the first substrate and defines a chamber surrounding the MEMS chip, and the third substrate is bonded to the second substrate and upwardly closes the chamber. A grid or mesh structure of electrically conductive material is formed in or on the third substrate and overlies the MEMS chip; the second substrate has a conductive connection structure coating the walls of the chamber, and the first substrate incorporates an electrically conductive region, which forms, together with the conductive layer and the grid or mesh structure, a Faraday cage.

BACKGROUND

1. Technical Field

The present disclosure regards an encapsulated micro-electro-mechanicaldevice, in particular a MEMS acoustic transducer, such as a microphone.

2. Description of the Related Art

As is known, microphones built in MEMS (micro-electro-mechanical system)technology generally comprise a first chip integrating a pressure sensorand a second chip integrating an electronic circuit for processingelectrical signals (read circuit). The two chips may be mounted on asupport and encapsulated in a package that mechanically protects thechips, above all the microphone, which is in itself fragile and verysubject to damage. Furthermore, the package may have metal structuresforming Faraday cages for eliminating electromagnetic interference.

Various types of package forming Faraday cages are known for integratedcircuits. For example, in some solutions, the package is formed by abase, on which a support for the chips is bonded, and by a cap solderedto the base. For example, the cap may have a metal coating, and the basemay be made of metal, being for instance formed by the lead frame forelectrically connecting chips (e.g., see “MEMS Packaging”, Bruce K. Galeet al., Oct. 11, 2001,http://www.mech.utah.edu/˜gale/mems/Lecture%2016b%20MEMS%20Packaging.pdf; and “Si-based Microphone Testing Methodology and Noisereduction”, C. S. Premachandran et al., Symposium on Design, Test,Integration, and Packaging of MEMS/MOEMS, Proceedings of SPIE Vol. 4019(2000))•0277-786X/OOI). Alternatively, the base may comprise metallayers, for example alternating with insulating materials (see, forexample, US 2007/071268; U.S. Pat. No. 6,781,231; U.S. Pat. No.7,166,910; EP 1 755 360; U.S. Pat. No. 7,434,305; US 2004/046 245; U.S.Pat. No. 7,436,054; U.S. Pat. No. 7,381,589; and WO2007/054070).

However, known solutions are either complex or costly, and thus leaveroom for improvement. In particular, in certain solutions it isproblematical to apply the metal coating via usual sputtering operationson account of the depth of the structures in the cap. Furthermore, inall cases, the process is costly and far from suited to devices, such asmicrophones, that are to be used in cell phones and the like, the costsof which should be as low as possible.

BRIEF SUMMARY

One embodiment of the present disclosure is an encapsulatedmicro-electro-mechanical device that overcomes the drawbacks of theknown art.

One embodiment is an encapsulated micro-electromechanical device thatincludes a MEMS chip and a package formed by first, second, and thirdsubstrates bonded to each other. The first substrate has an electricallyconducting region and a main surface carrying the MEMS chip. The secondsubstrate is bonded to the first substrate, defines a chambersurrounding the MEMS chip, and has a conductive connection structureextending transversely between the first and the third substrates. Thethird substrate is bonded to the second substrate, upwardly defines thechamber, and has a grid or mesh structure of electrically conductivematerial overlying the MEMS chip. The electrically conducting region,the conductive connection structure, and the grid or mesh structure areelectrically coupled to each other and form a Faraday cage.

One embodiment is a process for manufacturing a micro-electro-mechanicdevice. The process includes:

bonding a MEMS chip onto a first substrate incorporating an electricallyconducting region;

forming a chamber in a second substrate;

forming a conductive connection structure transversely to the secondsubstrate;

forming a grid or mesh structure of electrically conductive material ona third substrate;

bonding the third substrate to the second substrate so that the grid ormesh structure extends on the chamber; and

bonding the second substrate to the first substrate so that the chambersurrounds the MEMS chip, the chamber is enclosed between the third andthe first substrates, and the electrically conducting region iselectrically coupled to the conductive connection structure and to thegrid or mesh structure, forming a Faraday cage.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

For a better understanding of the present disclosure, preferredembodiments thereof are now described, purely by way of non-limitingexample, with reference to the attached drawings, wherein:

FIG. 1 shows a cross-section of an embodiment of the present MEMSacoustic transducer;

FIG. 2 is a bottom perspective view of the top part of the transducer ofFIG. 1;

FIGS. 3-12 show cross-sections of intermediate structures obtainedduring the manufacture of the transducer of FIG. 1, in successivemanufacturing steps of the manufacturing process;

FIG. 13 shows an enlarged cross-section of a variant of a detail of thetransducer of FIG. 1;

FIG. 14 shows a cross-section of a different embodiment of the presentencapsulated electronic transducer;

FIG. 15 shows a cross-section of another embodiment of the presenttransducer;

FIG. 16 shows a cross-section of a different embodiment of the presenttransducer;

FIG. 17 shows a cross-section of another embodiment of the presenttransducer;

FIG. 18 shows a partially sectioned bottom perspective view of a variantof the present transducer; and

FIG. 19 shows a general block diagram of an apparatus incorporating thepresent transducer.

DETAILED DESCRIPTION

With reference to FIGS. 1 and 2, a MEMS transducer 1 of an acoustic typecomprises a packaging 2 housing a microphone 3, manufactured in the MEMStechnology, and an integrated circuit 4, typically an ASIC(application-specific integrated circuit), formed by a semiconductormaterial chip integrating the reading electronics for amplifying andtreating the signal generated by the microphone 3. Hereinafter, themicrophone 3 and the integrated circuit 4 are also referred to as chips3, 4.

The microphone 3 comprises a structural layer 6 of semiconductormaterial, for example silicon, in which a cavity 7 is formed, forexample through chemical etching from the back. A diaphragm 8 is formedin, or coupled to, the structural layer 6 and upwardly closes the cavity7; the diaphragm 8 is flexible and, in use, undergoes deformation as afunction of the pressure of the incident sound waves. A rigid plate 9(generally known as “back-plate”) is arranged on top of the diaphragm 8and facing it. The back-plate 9 forms the fixed electrode of a detectioncapacitor with variable capacitance, the mobile electrode whereof isformed by the diaphragm 8, and has a plurality of holes (notillustrated), for enabling free circulation of air towards the diaphragm8 (in effect causing the back-plate 9 to be acoustically transparent).The microphone 3 further comprises (in a way not illustrated) electricalcontacts for biasing the diaphragm 8 and the back-plate 9 and picking upa capacitive variation signal resulting from the deformation of thediaphragm 8 caused by the incident acoustic pressure waves; in general,the electrical contacts are arranged in a surface portion of themicrophone chip 3.

The package 2 is formed by three parts: a bottom substrate 10, anintermediate substrate 11, and a top substrate 12, the top substrateforming, together with the intermediate substrate 11, a cap or lid forthe bottom substrate 10.

In detail, the bottom substrate 10 (having, for example, an overallthickness of 200 μm) is typically formed by one or more core layers ofinsulating material, typically plastic, in particular an epoxy resin,and specifically a BT (bismaleimide triazine) laminate or an FR-4laminate or other material of printed circuits. The bottom substrate 10comprises metal structures inside it. For example, the substrate maycontain a conductive layer 25, whether continuous or mesh-shaped orgrid-shaped. The bottom substrate 10 carries the microphone 3 and theintegrated circuit 4; consequently, adhesive regions (not illustrated)extend between a first surface 10 a of the bottom substrate 10 (facingthe intermediate substrate 11) and the chips 3, 4. Furthermore,conductive structures (not illustrated), such as conductive paths andcontact pads, are formed on the surface 10 a of the bottom substrate 10to enable electrical connection between the microphone 3, the integratedcircuit 4, and the outside. In the example illustrated, wires 28 a, 28 bconnect, respectively, the chips 3, 4 together and the microphone 3 withthe conductive structures (not illustrated) on the first surface 10 a ofthe bottom substrate 10 (paths, pads). Furthermore, a number ofconductive vias 16 extend through the bottom substrate 10, forconnecting conductive structures at the first surface 10 a withconductive structures at a second surface 10 b, on the back of the MEMStransducer 1 and at least one of them is grounded. Alternatively,conductive vias (not illustrated) may connect only the first surface 10a to the conductive layer 25, and at least one different conductive viaconnects the conductive layer 25 to the second surface 10 b and toground.

The intermediate substrate 11 is formed by an intermediate core layer13, also of BT, FR-4 or similar insulating material, drilled throughoutits thickness so as to define an internal cavity or chamber 14 housingthe chips 3, 4. The intermediate core layer 13 of the intermediatesubstrate 11 is coated with a metal layer 15, for example of copper,which coats at least the top surface, the bottom surface, and the wallof the chamber 14. The intermediate substrate 11 is moreover bonded tothe bottom substrate 10 through a first electrically conductive adhesivelayer 20, for example of conductive epoxy resin, for example with afiller of a metal material such as silver (Ag). The total thickness ofthe intermediate substrate 11 may be comprised between 500 and 600 μmand depends upon the height of the chip forming the microphone 3 and thefree space for connection of the wires 28 a, 28 b.

The top substrate 12 comprises a top core layer 21, which is also ofFR-4, BT or similar insulating material and is coated with a shieldlayer 22 of conductive material, typically metal, for example copper.The thickness of the shield layer may be for example 17 μm, and thetotal thickness of the top substrate 12 may be for example 60-100 μm.The shield layer 22 forms, over the chamber 14, a mesh or grid 24, asmay be seen in particular in FIG. 2. By the term “mesh or grid 24” isunderstood a non-continuous structure formed by portions or stretchescompletely connected together so that all the points of the mesh or gridare electrically connected together and at the same potential.

In FIG. 2, for example, the mesh or grid 24 has a series of holes 26,here square-shaped with sizes 100 μm×100 μm, arranged in an array,aligned in rows and columns and at a distance apart of for example 100μm.

The shield layer 22 is bonded to the intermediate substrate 11 through asecond adhesive layer 23, for example of conductive epoxy resin, likethe first adhesive layer 20. Furthermore, the mesh or grid 24 is coatedwith an insulating layer 27, for example a solder mask of polymericmaterial, such as resist, having a thickness of 20 μm.

In this way, the mesh or grid 24, together with the second adhesivelayer 23, the metal layer 15, the first adhesive layer 20, and theconductive layer 25, forms a Faraday cage 29, connected to groundthrough one or more vias 16, which electrostatically shields the chips3, 4, and uses a smaller amount of material than a continuous layer.

The top substrate 12 moreover has a hole 30 extending through the topcore layer 21, the mesh or grid 24, and the insulating layer 27 so as toput the chamber 14 in communication with the outside and enable entranceof the sound waves to be detected by the microphone 3.

The MEMS transducer 1 is manufactured as described with reference toFIGS. 3-10.

FIGS. 3-5 show the steps for manufacturing the intermediate substrate11. Initially (FIG. 3), a intermediate core wafer 13′ of insulatingmaterial is coated with a top metal layer 35 a and a bottom metal layer35 b of metal material, for example copper, with a thickness of, forexample, 25 μm. The coating may be obtained via lamination of a copperlayer on the intermediate core wafer 13′ or by sputtering and subsequentelectrolytic or electroless plating. Then (FIG. 4), the intermediatecore wafer 13′ is drilled using a purposely provided drilling tool, suchas a microdrill, in a per se known manner, so as to form a plurality ofchambers 14.

Next (FIG. 5), the exposed portions of the intermediate core wafer 13′(on the sides of the chambers 14) are coated via plating with metalmaterial, for example copper, forming, together with the top and bottommetal layers 35 a, 35 b, the metal layer 15. Alternatively, the lateralportions of the metal layer 15 (on the sides of the chambers 14) may beobtained by sputtering.

During, before, or after machining of the intermediate substrate 11, thetop substrate 12 is manufactured, as illustrated in FIGS. 6-9. In detail(FIG. 6), a top core wafer 21′ of insulating material (for example,FR-4, BT or the like) is coated on just one side with a shield layer22′, for example of laminated copper. Then (FIG. 7), using a resist mask(not illustrated) the portions of the shield layer 22′ that are to formthe mesh or grid portions 24 (on top of the chambers 14) are selectivelyetched, and resist is removed. Optionally, to facilitate the subsequentbonding between the intermediate substrate 11 and the bottom substrate10, plating may be carried out to form an auxiliary metal layer 35, forexample of Au or Ni, illustrated dashed only in FIG. 7.

Next (FIG. 8), an insulating layer is deposited, for example ofpolymeric material, such as resist (solder mask) with a thickness of 20μm, and is defined, so as to form the insulating layer 27 on the mesh orgrid portions 24, and to be removed from the portions of the shieldlayer 22′ that are to be bonded to the intermediate core wafer 13′.

Then (FIG. 9), the top core wafer 21′ is drilled so as to form aplurality of holes 30, one for each mesh or grid 24, and (FIG. 10) isbonded to the intermediate core wafer 13′, through a second adhesivelayer 23′. The structure of FIG. 10 thus obtained forms a cap wafer 36.

In the meantime (FIG. 11), a substrate wafer 10′ is provided, formed byone or more core layers and one or more conductive layers 25′ (in FIG.11, just one); the substrate wafer 10′ is drilled, and the holes aremetallized to form the vias 16, using the techniques known in theproduction of printed circuits. In this step, furthermore, conductivepaths and contact regions are formed on the surfaces 10 a and 10 b ofthe substrate wafer 10′. Then, the chips 3, 4 are bonded on thesubstrate wafer 10′, and the wires 28 a, 28 b are provided.

Next (FIG. 12), the cap wafer 36 is flipped over and fixed to thesubstrate wafer 10′ through a first adhesive layer 20′.

Finally, the composite wafer of FIG. 12 is diced to obtain a pluralityof MEMS devices 1 of FIG. 1.

FIG. 13 shows a variant of a detail of the MEMS transducer 1 of FIG. 1.Here, the bottom substrate 10 is of the multilayer type, including aplurality of core layers 40 of insulating material, e.g., BT or FR-4,arranged on each other, with conductive layers 41 extending betweenthem. The conductive layers 41 may be interrupted in overlying points soas to enable formation of vias 42; in the example illustrated, a via 42extends throughout the thickness of the bottom substrate 10 and connectsone of the top conductive regions 43 formed on the first surface 10 a toone of the bottom conductive regions 44 formed on the second surface 10b of the bottom substrate 10. The layers 41 are connected togetherthrough vias (not illustrated) and some of the conductive regions 43 and44 (insulated from the conductive regions 43 and 44 connected to thechips 3, 4) to create the ground connection of the Faraday cage 29.

A top insulation layer 46, for example a solder-mask layer, coats thefirst surface 10 a, and a bottom insulation layer 47, for example also asolder-mask layer, coats the second surface 10 b, with the exception ofthe conductive regions and 43, 44 that are to be connected to wires 28a, 28 b or where other contact structures (not illustrated), for exampleflip-chip solder bumps, for electrical connection to printed circuits,are to be provided, in a per se known manner.

In the detail illustrated in FIG. 13, the integrated circuit 4 isbonded, via an adhesive layer 48, on the top insulation layer 46.

The conductive layers 41 may be of a continuous type (except for at thevias 42) or may have a mesh configuration, such as the mesh or grid 24of FIG. 1 or 2 or as discussed hereinafter with reference to FIGS. 17,18.

FIG. 14 shows an embodiment where a hole 50 is formed in the bottomsubstrate 10 under the microphone 3 so as to enable the waves acousticto reach the microphone 3 and be detected thereby.

In FIG. 15, the intermediate substrate 11 has vias 55 of conductivematerial that connect the top metal layer 35 a to the bottom metal layer35 b. Here, the side walls of the chamber 14 are not coated with metalmaterial, and the vias 55 contribute to forming a Faraday cage with themesh or grid 24 and the conductive layer 25. The vias 55 may be obtainedby drilling the intermediate substrate 11 during drilling of thechambers 14 or in a separate step to form openings that surround thechambers 14 and then filling the openings thus obtained with metalmaterial. The vias 55 here do not form a continuous wall, as in theembodiment of FIGS. 1-12, but are effective in forming a Faraday cage.Alternatively, only the walls of the vias 55 may be metallized, leavingthe inside empty or filling it with even non-conductive material, suchas resin, which is of lower cost. According to yet another alternative,if the vias 55 are formed prior to formation of the chamber 14 andduring drilling of the chamber, the wall of the latter traverses one ormore vias 55, half of which are removed, leaving half of the via or vias55 facing the inside of the chamber 14 (in this case, the cross-sectionthrough the package 2 is similar to that of FIG. 1).

Furthermore, in the example illustrated, the electrical connectionbetween the first adhesive layer 20 and the conductive layer 25 in thebottom substrate 10 is direct. For example, by forming the top layer(designated by 61 in FIG. 15) of the bottom substrate 10 with soldermask or other non-conductive material that may be shaped via chemicaletching, the top layer 61 may be selectively removed in some points, sothat when the first adhesive layer 20 is laid, this directly contactsthe conductive layer 25 in the removed points of the top layer 61. Inthis case, vias 18 connect the conductive layer 25 with the secondsurface 10 b of the bottom substrate to enable connection to ground.

In FIG. 15, the hole 30 is formed in the top substrate 12, but could beformed in the bottom substrate 10, as in FIG. 14.

FIG. 16 shows a MEMS transducer 1, where the connection of the chips 3,4 with the outside is made through the top substrate 12, as described indetail in patent application No. TO2009A0001036, filed on Dec. 23, 2009.In detail, here the top core layer 21 has vias 58 that connect togetherits main faces and are aligned vertically and to conductive regions 57(paths and/or contact pads) on one side and to conductive portions 22 aof the shield layer 22. The wire 28 b electrically connects theintegrated circuit 4 with a conductive portion 22 a of the shield layer22. To electrically insulate the conductive portion 22 a from the secondadhesive layer 23 and from the metal layer 15, the top metal layer 35 aand the second adhesive layer 23 are defined before being bondedtogether so as to form portions 15 a electrically insulated from therest of the metal layer 15 and adhesive portions 23 a electricallyinsulated from the rest of the second adhesive layer 23.

In practice, before forming the shield layer 22′, the top core layer 21is drilled, and the holes thus obtained are filled with conductivematerial (for example copper) to form the vias 57. Also in this case, itis possible to coat only the walls of the holes or of the vias, thusobtaining empty cylindrical connections or connections filled withnon-conductive material such as resin. The conductive regions 57 on themain face of the top core layer 21 are formed of metal such as Cu, Ni,Au, and the conductive portions 22 a are formed while defining theshield layer 22′ to obtain the grid or mesh regions 24. Likewise, duringdefinition of the top metal layer 35 a and of the second adhesive layer23′, the adhesive portions 23 a and the portions 15 a of the top metallayer 35 a are formed.

FIG. 17 shows an embodiment where the mesh or grid 24 is provided viainterwoven wires 60 embedded in the material of the top core layer 21.In this case, the mesh or grid 24 is formed preliminarily and theninserted in the top core layer 21 during a co-moulding step. Vias 59connect the mesh or grid 24 to the second adhesive layer 23.

According to another embodiment, the mesh or grid 24 is formed byinterwoven wires 60 and is fixed to the top core layer 21, for exampleusing a third adhesive layer 61. In this case, the mesh or grid 24extends laterally with respect to the hole 30 and thus does not coverthe integrated circuit 4. Alternatively, a hole may be made in thebottom substrate 10, as illustrated in FIG. 14, and in this case themesh or grid 24 may coat both of the chips 3, 4. In a way notillustrated, the mesh or grid 24 may extend as far as the intermediatesubstrate 11 so as to contact the second adhesive layer 23, or elseconductive paths may be provided for connecting the mesh or grid 24electrically to the second adhesive layer 23.

The MEMS transducer 1 described herein has numerous advantages.

In particular, the mesh or grid 24 enables reduction of the amount ofmetal material used to obtain the shielding, though operatingeffectively according to the principle of a Faraday cage. In fact, evenwhen the mesh or grid 24 is formed by etching a deposited or grownlayer, the removed material may be recovered and re-used. The savingobtained by the lower metal consumption is only in part compensated forby the production steps necessary for forming or bonding the mesh orgrid 24. It follows that the finished MEMS transducer has lower costs.

Furthermore, the insulating layer 27 prevents the mesh or grid 24 frombeing shorted with the wires 28 a, 28 b, and/or other conductivestructures within the chamber 14 because of the inevitable mechanicaldeformation of the structure, in particular of the top substrate 12, andof the small spaces.

The characteristics listed previously render particularly advantageousthe use of the MEMS acoustic transducer 1 in an electronic apparatus 70,as illustrated in FIG. 19. The electronic apparatus 70 is preferably amobile communications device, such as for example a cell phone, a PDA, anotebook, but also a voice recorder, an audio-file reader withvoice-recording capacity, etc. Alternatively, the electronic apparatus70 may be a hydrophone, which is able to work under water, or else ahearing-aid device.

The electronic apparatus 70 comprises a microprocessor (CPU—centralprocessing unit) 71, a memory block 72, connected to the microprocessor71, and an input/output interface 73, for example equipped with akeyboard and a display, which is also connected to the microprocessor71. The transducer 1 communicates with the microprocessor 71. Inparticular, the ASIC 4 sends the electrical output signals to themicroprocessor 71 (a further electronic circuit may also be provided forprocessing the electrical output signals, designated by 75).Furthermore, a loudspeaker 76 is present for generation of sounds on anaudio output (not illustrated) of the electronic apparatus 70. Asillustrated schematically, the transducer 1, the microprocessor 71, thememory block 72, the input/output interface 73, and the possible furtherelectronic components are coupled to a single printed circuit board 77,for example with the SMD (surface-mount device) technique.

Finally, it is clear that modifications and variations may be made tothe MEMS transducer and to the manufacturing method described andillustrated herein, without thereby departing from the scope of thepresent disclosure.

For example, in the embodiment of FIG. 13, instead of just one via 42extending through the entire thickness of the bottom substrate 10, it ispossible to use two or more partial vias, which connect a respectiveface of the bottom substrate 10 to a conductive region 25 and/or toconductive regions 25, 40 together, in a per se known manner in thesector of printed-circuit boards.

The contact between the conductive layer 25 (and possibly the conductivelayers 41) may be obtained in any one of the ways described for all theillustrated embodiments. Consequently, irrespective of the number ofconductive layers 25, 41, the position of the hole 30 or 50, thepresence or not of vias 33 in the intermediate substrate 11 or of thelayer 15 coating the walls of the chamber 15, and the configuration ofthe mesh or grid 24, it is possible to provide vias 16 or 42 or 18and/or contact directly the conductive layer 25 with the first adhesivelayer 20.

Furthermore, in the case where the MEMS chip 3 incorporates the readcircuits, the MEMS transducer 1 could house just the chip 3, and thiswould be connected directly via the wires 28 a with the outside, throughthe first substrate 10 or the third substrate 12, without the need toprovide a separate ASIC 4.

The various embodiments described above can be combined to providefurther embodiments. All of the U.S. patents, U.S. patent applicationpublications, U.S. patent application, foreign patents, foreign patentapplication and non-patent publications referred to in thisspecification are incorporated herein by reference, in their entirety.Aspects of the embodiments can be modified, if necessary to employconcepts of the various patents, application and publications to provideyet further embodiments.

These and other changes can be made to the embodiments in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the claims to the specificembodiments disclosed in the specification and the claims, but should beconstrued to include all possible embodiments along with the full scopeof equivalents to which such claims are entitled. Accordingly, theclaims are not limited by the disclosure.

1. An encapsulated micro-electro-mechanical device, comprising: a MEMSchip; and a package having first, second, and third substrates bonded toeach other, the first substrate having an electrically conductive regionand a main surface carrying the MEMS chip; the second substrate beingbonded to the first substrate, defining a chamber surrounding the MEMSchip, and having a conductive connection structure extendingtransversely between the first and the third substrates; and the thirdsubstrate being bonded to the second substrate, upwardly defining thechamber, and having a grid or mesh structure of electrically conductivematerial overlying the MEMS chip; the electrically conductive region,the conductive connection structure, and the grid or mesh structurebeing electrically coupled to each other and forming a Faraday cage. 2.A device according to claim 1, wherein the first, the second and thethird substrates comprise respective first, second, and third corelayers of insulating material, wherein the first core layer accommodatesthe electrically conductive region; the conductive connection structureis supported by the second core layer; and the grid or mesh structure isembedded in, or extends on, the third core layer.
 3. A device accordingto claim 2, wherein the conductive connection structure coats a wall ofthe second core layer and delimits the chamber or forms conductive viasextending through the second core layer.
 4. A device according to claim2, wherein the grid or mesh structure extends on the chamber andincludes a shield layer of conductive material extending on a first faceof the third core layer facing the first and the second substrates.
 5. Adevice according to claim 4, further comprising an insulating layer thatcoats the grid or mesh structure.
 6. A device according to claim 4,wherein the grid or mesh structure includes a mesh of metal wiresmutually interwoven, the mesh of metal wires being embedded in the thirdcore layer or bonded on the first face of the third core layer facingthe first and the second substrates.
 7. A device according to claim 4,further comprising: a first conductive portion extending on the firstface of the third core layer and insulated from the shield layer; asecond conductive portion electrically coupled to the first conductiveportion, sandwiched between the second and the third substrates, andinsulated from the conductive connection structure; a through viaextending through the third core layer and in electric contact with thefirst conductive portion; a third conductive portion extending on asecond face of the third core layer not facing the second substrate; anda wire coupling the MEMS chip to the first conductive portion.
 8. Adevice according to claim 1, wherein the electrically conductive regionin the first substrate is shaped as a mesh or grid.
 9. A deviceaccording to claim 1, wherein the first substrate comprises a pluralityof core layers of insulating material and a plurality of electricallyconductive regions, the plurality of core layers being interleaved withthe plurality of electrically conductive regions.
 10. A device accordingto claim 1, wherein the MEMS chip includes an integrated microphone, thedevice further comprising an ASIC integrated circuit carried by thefirst substrate and electrically coupled to the MEMS chip.
 11. A processfor manufacturing a micro-electro-mechanic device, comprising: bonding aMEMS chip onto a first substrate incorporating an electricallyconducting region; forming a chamber in a second substrate; forming aconductive connection structure transversely to the second substrate;forming a grid or mesh structure of electrically conductive material ona third substrate; bonding the third substrate to the second substrateso that the grid or mesh structure extends on the chamber; and bondingthe second substrate to the first substrate so that the chambersurrounds the MEMS chip, the chamber is enclosed between the third andthe first substrates, and the electrically conducting region iselectrically coupled to the conductive connection structure and to thegrid or mesh structure, forming a Faraday cage.
 12. A process accordingto claim 11, wherein forming the grid or mesh structure comprisesforming a metal layer on a surface of a core layer of the thirdsubstrate and removing selective portions of the metal layer.
 13. Aprocess according to claim 12, further comprising coating the grid ormesh structure with an insulating layer.
 14. A process according toclaim 11, wherein forming the grid or mesh structure comprises forming amesh of metal wires mutually interwoven and bonding the mesh of metalwires to the third substrate or incorporating the mesh of metal wires inthe third substrate.
 15. A process according to claim 11, furthercomprising forming an external communication hole opening onto thechamber in the first or in the third substrate before bonding the secondsubstrate to the first substrate or before bonding the third substrateto the second substrate.
 16. A process according to claim 11, whereinforming the chamber and forming the conductive connection structurecomprise coating first and second faces of an intermediate core layerwith metal material; drilling the intermediate core layer to form thechamber and coating lateral walls of the chamber with further metalmaterial.
 17. A process according to claim 11, wherein forming theconductive connection structure comprises forming conductive vias byforming apertures in an intermediate core layer, the aperturessurrounding the chamber, and filling the apertures with metal material.18. A process according to claim 11, wherein bonding the third substrateto the second substrate comprises bonding the first face of the secondsubstrate to the third substrate through the conductive connectionstructure and a conductive adhesive layer.
 19. An apparatus, comprising:a processor; and an encapsulated micro-electro-mechanical device thatincludes: a MEMS chip; and a package having first, second, and thirdsubstrates bonded to each other, the first substrate having anelectrically conductive region and a main surface carrying the MEMSchip; the second substrate being bonded to the first substrate, defininga chamber surrounding the MEMS chip, and having a conductive connectionstructure extending transversely between the first and the thirdsubstrates; and the third substrate being bonded to the secondsubstrate, upwardly defining the chamber, and having a grid or meshstructure of electrically conductive material overlying the MEMS chip;the electrically conductive region, the conductive connection structure,and the grid or mesh structure being electrically coupled to each otherand forming a Faraday cage.
 20. An apparatus according to claim 19,wherein the first, the second and the third substrates compriserespective first, second, and third core layers of insulating material,wherein the first core layer accommodates the electrically conductiveregion; the conductive connection structure is supported by the secondcore layer; and the grid or mesh structure is embedded in, or extendson, the third core layer.
 21. An apparatus according to claim 20,wherein the conductive connection structure coats a wall of the secondcore layer and delimits the chamber.
 22. An apparatus according to claim20, wherein the grid or mesh structure extends on the chamber andincludes a shield layer of conductive material extending on a first faceof the third core layer facing the first and the second substrates, thedevice including an insulating layer that coats the grid or meshstructure.
 23. An apparatus according to claim 20, wherein the deviceincludes: a first conductive portion extending on a first face of thethird core layer and insulated from the shield layer; a secondconductive portion electrically coupled to the first conductive portion,sandwiched between the second and the third substrates, and insulatedfrom the conductive connection structure; a through via extendingthrough the third core layer and in electric contact with the firstconductive portion; a third conductive portion extending on a secondface of the third core layer not facing the second substrate; and a wirecoupling the MEMS chip to the first conductive portion.
 24. An apparatusaccording to claim 19, wherein the grid or mesh structure includes amesh of metal wires mutually interwoven.
 25. An apparatus according toclaim 19, wherein the first substrate comprises a plurality of corelayers of insulating material and a plurality of electrically conductiveregions, the plurality of core layers being interleaved with theplurality of electrically conductive regions.
 26. An apparatus accordingto claim 19, wherein the MEMS chip includes an integrated microphone,the device further comprising an ASIC integrated circuit carried by thefirst substrate and electrically coupled to the MEMS chip.